JP5047026B2 - Turbo type vacuum pump - Google Patents

Description

  The present invention relates to a turbo vacuum pump, and more particularly to an oil-free turbo vacuum pump that can be evacuated from atmospheric pressure to high vacuum.

  Conventionally, in a semiconductor manufacturing apparatus or the like, a turbo type vacuum pump is used to exhaust a gas in a chamber to obtain a clean high vacuum (or ultra-high vacuum). In this turbo vacuum pump, a turbo molecular pump stage, a thread groove pump stage and a vortex pump stage are sequentially arranged in a pump housing having an intake port and an exhaust port, and a rotary shaft to which the rotor blades of these pump stages are fixed. Is supported by a hydrostatic gas bearing, or a multistage centrifugal compression pump stage is installed in a pump housing having an intake port and an exhaust port. There are vacuum pumps of the type supported by bearings and thrust gas bearings. In this way, by using a gas bearing to support the rotating shaft without using a rolling bearing, an oil-free turbo that does not require oil to be used not only for the gas flow path but also for the entire pump including the bearing portion and the like. Type vacuum pump.

JP 2002-285987 A Japanese Utility Model Publication 1-14-2594

  A turbo vacuum pump that combines the above-described turbo molecular pump stage, thread groove pump stage, vortex pump stage, and static pressure gas bearing is described in, for example, Japanese Patent Application Laid-Open No. 2002-285987 (Patent Document 1). This vacuum pump can compress gas from ultra-high vacuum to atmospheric pressure. The vortex pump (circumferential flow wing) of the vortex pump stage is a wing element that can compress gas to atmospheric pressure even if the wing clearance is wide, and a rotating wing that is formed radially around the rotating disk, It is comprised from the annular recessed part (ventilation path) which covers the rotating disc in which the wing | blade was formed, and the communicating path which connects the ventilation path adjacent to the upper and lower sides. The vortex blade has a drawback that the volume of the blade element is large because an air passage that covers the rotating disk up and down is necessary. Also, because of the structure that sucks gas from the communication passage (suction port) provided in one place in the ventilation path, compresses it in the circumferential direction, and discharges it from the communication path (discharge port) communicating with the adjacent ventilation path, the exhaust speed There is a disadvantage that (exhaust capacity) is small. Furthermore, since a rotating disk having a plurality of radially formed rotor blades is rotated in the atmospheric pressure region, there is a drawback that the driving power is large. In addition, there is a structural problem that the structure on the fixed side where the ventilation path and the communication port are formed is complicated.

  A turbo type vacuum pump in which the above-described centrifugal compression pump stage and a gas bearing are combined is described in, for example, Japanese Utility Model Publication No. 1-142594 (Patent Document 2). Compressible to near atmospheric pressure. In this vacuum pump, the thrust gas bearing is installed on the exhaust port side, and the rotation-side thrust disk of the thrust gas bearing is configured to be sandwiched in the axial direction by the upper and lower disks on the fixed side. This vacuum pump has a disadvantage that the number of parts is large because the centrifugal compression pump stage and the gas bearing are separate structures. And since a centrifugal compression pump stage and a gas bearing are separate structures, there exists a problem that miniaturization of the wing clearance of a centrifugal compression pump stage is difficult.

  The present invention has been made in view of the above points, and is a wing element capable of compressing a gas from a high vacuum to an atmospheric pressure, and has a simple structure and a highly efficient (small driving power) wing element. The object is to provide a pump.

  In order to achieve the above-mentioned object, one aspect of the present invention includes a rotating shaft extending over substantially the entire length of a pump, an exhaust section formed by alternately arranging rotating blades and fixed blades in a casing, In a turbo type vacuum pump having a bearing motor section having a motor for applying a rotational driving force to the rotating shaft and a bearing for rotatably supporting the rotating shaft, a gas bearing is provided on the bearing for supporting the rotating shaft in a thrust direction. The spiral groove is formed on both surfaces of the fixed side portion of the gas bearing, and the fixed side portion where the spiral groove is formed by the upper rotating side portion and the lower rotating side portion fixed to the rotating shaft. The centrifugal blade element for compressing and exhausting gas in the radial direction is formed on the surface opposite to the surface facing the spiral groove on the upper rotation side portion.

  According to the present invention, a gas bearing is used as a bearing for supporting a rotating body including a rotating shaft and a rotating blade fixed to the rotating shaft in the thrust direction. It can be rotated and held with an accuracy of 10 microns (μm). A centrifugal blade element that compresses the gas in the radial direction is integrally formed at a portion on the rotating body side that constitutes the gas bearing, that is, an upper rotation side portion. Since the direction of the minute clearance of the gas bearing and the centrifugal blade is the same thrust direction, the blade clearance of the centrifugal blade element can be set substantially equal to the clearance of the gas bearing (or slightly larger than the clearance of the gas bearing). That is, since the centrifugal blade element that compresses the gas in the radial direction is formed in the upper rotation side portion, the upper rotation side portion constitutes the centrifugal blade and constitutes a part of the gas bearing that performs axial positioning. Will do. As described above, since the centrifugal blade element that compresses the gas in the radial direction is formed in the upper rotation side portion that is positioned in the axial direction, the blade clearance of the centrifugal blade element can be accurately controlled.

In a preferred embodiment of the present invention, centrifugal blade elements that compress and exhaust gas in the radial direction are arranged in multiple stages in the axial direction, and the blade clearance of the centrifugal blade elements is set to gradually increase from the exhaust side toward the intake side. It is characterized by that.
In order to compress gas from ultra-high vacuum to atmospheric pressure, it is necessary to increase the number of blades. Here, when the temperatures of the rotor blades and the stationary blades are compared, the temperature on the rotor blade side is naturally higher. Therefore, if the clearance of each stage is the same when multistage, the difference in thermal expansion between the rotating blade and the fixed blade occurs due to this temperature difference, and the clearance on the upstream side is gradually narrowed, and contact may occur. . For this reason, the blade clearance at each stage must be adjusted in consideration of this temperature difference. However, since the blade clearance at each stage is very small, measuring and adjusting the clearances at all stages is very laborious and causes an increase in assembly time. Therefore, as in the present invention, it is preferable to set the blade clearance so that it gradually increases from the exhaust side toward the intake side.

According to a preferred aspect of the present invention, centrifugal blade elements for compressing and exhausting gas in the radial direction are arranged in multiple stages in the axial direction, and the axis of the fixed blade with respect to the axial thickness of the rotor blade having the centrifugal blade element. The directional thickness is about 10 to 50% thicker than the blade clearance formed in the axial direction.
According to the present invention, by setting the axial thickness on the fixed blade side to be thicker than that on the rotary blade side in advance, the blade clearance naturally increases each time the number of stages is increased. For example, if the axial thickness on the stationary blade side is set to be t μm thicker than the axial thickness on the rotor blade side, and the blade clearance of the centrifugal blade stage closest to the gas bearing is assumed to be CLμm, The blade clearance is CL μm + t μm, and the blade clearance of the next stage is CL μm + 2 × t μm. As the number of stages is increased, the blade clearance naturally increases. This dimensional difference may be determined in consideration of the temperature difference between the rotary blade side and the fixed blade side. In addition, if the material of the rotary blade and the fixed blade are different, the difference in their linear expansion coefficients may be taken into consideration.

In a preferred aspect of the present invention, the centrifugal blade groove of the centrifugal blade element that compresses and exhausts gas in the radial direction is formed on both the surface forming the minute clearance in the axial direction on the rotor blade side and the surface on the opposite side. And
In order to increase the number of wings with minute clearances, the accuracy of each part has never been as high as possible. A centrifugal blade element composed of a centrifugal blade groove that compresses and exhausts gas in the radial direction is formed on a surface that exhausts gas from the inner peripheral side to the outer peripheral side. That is, the centrifugal blade element is formed in the direction in which the centrifugal force acts. However, when the centrifugal blade element is formed only on one side, the centrifugal blade surface is likely to be bent and deformed, and the surface needs to be corrected.
According to the present invention, on the rotor blade side, the same centrifugal blade groove is formed on the surface on the opposite side where the centrifugal blade groove is formed, thereby reducing the bending and deformation of the surface.

A preferred aspect of the present invention is characterized in that an elastically deformable structure portion is provided in at least a part of a component for fastening the centrifugal blade elements arranged in multiple stages in the axial direction.
In the turbo type vacuum pump of the present invention, ceramics are suitable as a material for each component because a very small blade clearance is formed. Silicon nitride ceramics having high strength are suitable for the rotor blade side, and silicon carbide ceramics having high thermal conductivity are suitable for the fixed blade side. In addition, alumina ceramics can also be used on the fixed blade side. Stainless steel (martensitic stainless steel) when a material with a small coefficient of linear expansion (about 3 x ^10-6 / ° C) such as ceramics is used for the rotor blade and stainless steel (martensitic stainless steel) is used for the rotating shaft. Since the linear expansion coefficient is about 10 × 10 ⁻⁶ / ° C., there is a risk that loosening of the fastening may occur during temperature rise due to rotation of the rotating body due to the difference in linear expansion coefficient.
According to the present invention, the elastic deformation structure portion is provided in at least a part of the parts for fastening the centrifugal blade elements arranged in multiple stages in the axial direction. By generating the deformation in the axial direction, it is possible to prevent loosening due to thermal deformation. As a material of the elastic deformation structure portion, an aluminum alloy is suitable.

The present invention has the following effects.
(1) A gas bearing is used as a bearing for supporting a rotating body including a rotating shaft and a rotating blade fixed to the rotating shaft in the thrust direction, and a part on the rotating body side constituting the gas bearing, that is, an upper rotating side part In addition, by forming the centrifugal blade element that compresses the gas in the radial direction integrally, the direction of micro clearance of the gas bearing and the centrifugal blade is the same thrust direction, so the blade clearance of the centrifugal blade element is the clearance of the gas bearing. Can be set almost the same. Therefore, the blade clearance of the centrifugal blade element can be accurately controlled.
(2) Since the blade clearance of the centrifugal blade elements arranged in multiple stages in the axial direction is set so as to gradually increase from the exhaust side to the intake side, the thermal expansion difference between the rotating blade and the fixed blade is caused by the temperature difference. If there is a phenomenon that the upstream clearance gradually narrows, there is no risk of contact between the rotor blades and fixed blades, and the blade clearance of each stage must be measured and adjusted in consideration of this temperature difference. Therefore, the assembly time can be shortened.
(3) By setting the axial thickness on the fixed blade side to be thicker in advance than the axial thickness on the rotor blade side, the blade clearance can be increased naturally each time the number of stages is increased. No adjustment is required.
(4) Since the centrifugal blade groove of the centrifugal blade element that compresses and exhausts gas in the radial direction is formed on both the surface that forms the minute clearance in the axial direction on the rotor blade side and the surface on the opposite side, the bending and deformation of the surface Can be reduced, and the surface need not be corrected.
(5) An elastically deformable structure portion is provided in at least a part of components for fastening the centrifugal blade elements arranged in multiple stages in the axial direction. When the rotor blade is fastened in the axial direction, By causing the deformation to occur, it is possible to prevent loosening due to thermal deformation.

  Hereinafter, an embodiment of a turbo vacuum pump according to the present invention will be described with reference to FIGS. 1 to 12, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a longitudinal sectional view showing an embodiment of a turbo vacuum pump according to the present invention. As shown in FIG. 1, the turbo vacuum pump includes a rotary shaft 1 extending over substantially the entire length of the pump, and an exhaust unit 10 formed by alternately arranging rotary blades and fixed blades in a casing 2. A bearing motor unit 50 having a motor that applies a rotational driving force to the rotary shaft 1 and a bearing that rotatably supports the rotary shaft is provided. The casing 2 includes an upper casing 3 that accommodates the exhaust portion 10 and a lower casing 4 that accommodates the bearing motor portion 50, and an intake port 5 is formed at the upper end portion of the upper casing 3. An exhaust port 6 is formed in the lower part of the.

  The exhaust part 10 is configured by sequentially arranging a turbine blade exhaust part 11, a first centrifugal blade exhaust part 21, and a second centrifugal blade exhaust part 31 from the inlet side of the upper casing 3 downward. The turbine blade exhaust section 11 includes a turbine blade 12 as a multistage rotor blade, and a multistage stationary blade 17 disposed immediately downstream of the turbine blade 12. The multistage turbine blade 12 is formed integrally with a substantially cylindrical turbine blade portion 13, and a hollow portion 15 is formed in a boss portion 14 of the turbine blade portion 13. A through hole 15h is formed in the bottom 15a of the hollow portion 15, and a bolt 16 is inserted into the through hole 15h. That is, the turbine blade portion 13 is fixed to the rotary shaft 1 by inserting the bolt 16 through the through hole 15 h and screwing it into the screw hole 1 s at the top of the rotary shaft 1.

On the other hand, the multistage fixed wings 17 are fixed in the upper casing 3 by being sandwiched by spacers 18 stacked in the upper casing 3. Thereby, in the turbine blade exhaust part 11, the turbine blades 12 as the rotating blades and the fixed blades 17 are alternately arranged.
The first centrifugal blade exhaust unit 21 includes a centrifugal blade 22 as a multistage rotating blade and a multistage stationary blade 23 disposed on the flow side immediately after the centrifugal blade 22. The centrifugal blades 22 are stacked in multiple stages and are fitted to the outer periphery of the rotary shaft 1, and are fixed to the rotary shaft 1 by a fixing means such as a key. The fixed wings 23 are also stacked in the upper casing 3 in multiple stages. Thereby, in the 1st centrifugal blade exhaust part 21, it has the structure by which the centrifugal blade 22 as a rotary blade and the fixed blade 23 are arrange | positioned alternately. Each centrifugal blade 22 has a centrifugal blade element 22a composed of a centrifugal blade groove that compresses and exhausts gas in the radial direction.

  The second centrifugal blade exhaust unit 31 includes a centrifugal blade 32 as a multistage rotating blade, and a multistage stationary blade 33 disposed immediately downstream of the centrifugal blade 32. The centrifugal blades 32 are stacked in multiple stages and are fitted to the outer periphery of the rotating shaft 1, and are fixed to the rotating shaft 1 by a fixing means such as a key. The fixed wings 33 are also laminated in the upper casing 3 in multiple stages. Thereby, in the 2nd centrifugal blade exhaust part 31, it has the structure by which the centrifugal blade 32 as a rotary blade and the fixed blade 33 are arrange | positioned alternately. Each centrifugal blade 32 has a centrifugal blade element 32a formed of a centrifugal blade groove that compresses and exhausts gas in the radial direction. A gas bearing 40 that supports the rotating body including the rotating shaft 1 and the rotating blades 12, 22, and 32 fixed to the rotating shaft 1 in the thrust direction is provided immediately downstream of the second centrifugal blade exhaust portion 31. ing.

  FIG. 2 is an enlarged view of a main part showing the gas bearing 40 and its peripheral part. As shown in FIG. 2, the gas bearing 40 is arranged so that the fixed side member (fixed side part) 41 fixed to the upper casing 3 and the upper side rotation arranged so as to sandwich the fixed side member (fixed side part) 41 therebetween. It is composed of a side member (upper rotation side part) 42 and a lower rotation side member (lower rotation side part) 43. The upper rotation side member (upper rotation side part) 42 and the lower rotation side member (lower rotation side part) 43 are fixed to the rotary shaft 1. Spiral grooves 45, 45 are formed on both surfaces of the fixed side member (fixed side portion) 41. Formation of spiral grooves 45, 45 by members (parts) divided into upper and lower parts on the rotation side, that is, upper rotation side member (upper rotation side part) 42 and lower rotation side member (lower rotation side part) 43. The fixed side member (fixed side portion) 41 is sandwiched. The upper rotating side member (upper rotating side portion) 42 includes a centrifugal blade element that compresses and exhausts gas in the radial direction on a surface opposite to the surface facing the spiral groove 45 of the fixed side member (fixed side portion) 41. 42a is formed. The centrifugal blade element 42a includes a centrifugal blade groove that compresses and exhausts gas in the radial direction.

  3 is a view taken in the direction of arrow III in FIG. As shown in FIG. 3, a large number of spiral grooves 45 are formed on the surface of the fixed side member (fixed side part) 41 (in FIG. 3, only some spiral grooves are shown). .

  As shown in FIG. 2, by adopting a gas bearing 40 as a bearing for supporting a rotating body including a rotating shaft 1 and a rotating blade fixed to the rotating shaft 1 in a thrust direction, the rotating body is axially several microns ( It becomes possible to rotate and hold with an accuracy of from μm) to several tens of microns (μm). A centrifugal blade element 42a for compressing the gas in the radial direction is formed integrally with a portion on the rotating body side constituting the gas bearing 40, that is, an upper rotation side member (upper rotation side portion) 42. Since the direction of minute clearance between the gas bearing 40 and the centrifugal blade is the same thrust direction, the blade clearance of the centrifugal blade element 42a can be set substantially equal to the clearance of the gas bearing 40 (or slightly larger than the clearance of the gas bearing). is there. That is, since the centrifugal blade element 42a for compressing the gas in the radial direction is formed in the upper rotational member (upper rotational portion) 42, the upper rotational member (upper rotational portion) 42 constitutes a centrifugal blade. In addition, a part of the gas bearing 40 for axial positioning is formed. Thus, since the centrifugal blade element 42a that compresses the gas in the radial direction is formed in the upper rotation side member (upper rotation side portion) 42 that positions in the axial direction, the blade clearance of the centrifugal blade element 42a is accurate. It can be controlled well.

The clearance of the gas bearing 40 when the rotating body including the rotating shaft 1 and the rotating blade fixed to the rotating shaft 1 is floating at the axial center of the gas bearing 40 is δd, and the blade clearance at that time is δe. The difference between δe and δd (δe−δd) is set to about 10 to 30% of the total clearance 2δd (that is, δdu + δdl) of the gas bearing 40 in terms of the reliability with respect to the contact of the blade and the exhaust performance of the blade. Is appropriate. That is, it is preferable to set δe−δd = (0.1 to 0.3) × (2δd).
In FIG. 2, since the state where the rotating body is floating at the center of the gas bearing 40 in the axial direction is illustrated, δdu (= δd) and δdl (= δd) are set.
The reason why the performance of the turbo blade element is poor in the atmospheric pressure region is that the blade clearance is large and the backflow increases in the atmospheric pressure region. With the structure of the present invention, the blade clearance can be miniaturized and the compression performance can be greatly improved in the atmospheric pressure region.

  In the turbo vacuum pump of this embodiment, the centrifugal blade elements 42a, 32a, 22a for compressing and exhausting gas in the radial direction are arranged in multiple stages in the axial direction, and the blade clearance of the centrifugal blade elements 32a, 22a is It is set to gradually increase from the exhaust side toward the intake side. In order to compress gas from ultra-high vacuum to atmospheric pressure, it is necessary to increase the number of blades. Here, when the temperatures of the rotor blades and the stationary blades are compared, the temperature on the rotor blade side is naturally higher. Therefore, if the clearance of each stage is the same when multistage, the difference in thermal expansion between the rotating blade and the fixed blade occurs due to this temperature difference, and the clearance on the upstream side is gradually narrowed, and contact may occur. . For this reason, the blade clearance at each stage must be adjusted in consideration of this temperature difference. However, since the blade clearance at each stage is very small, measuring and adjusting the clearances at all stages is very laborious and causes an increase in assembly time. Therefore, it is preferable to set the blade clearance so as to gradually increase from the exhaust side toward the intake side.

  FIG. 4 is an enlarged view of the main part showing the exhaust part set so that the blade clearance gradually increases from the exhaust side toward the intake side. With reference to FIG. 4, the relationship of blade clearance when the number of centrifugal blade stages is assumed to be five will be described. A symbol representing the number of stages of the centrifugal blades is denoted by n, the centrifugal blade stage closest to the gas bearing 40 is n = 1, and the blade clearance is δe1. The blade clearance is δe1 to δe5, and the relationship is set to δe1 ≦ δe2 ≦ δe3 ≦ δe4 ≦ δe5. (However, all blade clearances are equal, except for δe1 = δe2 = δe3 = δe4 = δe5)

FIG. 4 shows the relationship of the axial thickness of the fixed blade with respect to the axial thickness of the rotor blade of the centrifugal blade element. As shown in FIG. 4, in the turbo vacuum pump of this embodiment, centrifugal blade elements that compress and exhaust gas in the radial direction are arranged in multiple stages in the axial direction, and the axial thickness of the rotary blades of the centrifugal blade element is set. On the other hand, the axial thickness of the fixed blade is about 10 to 50% thicker than the blade clearance formed in the axial direction. That is, the axial thickness of the rotor blades (the upper rotary member 42, the centrifugal blade 32, and the centrifugal blade 22) having the centrifugal blade elements in the exhaust unit 10 is Hr, and the axial thicknesses of the fixed blades 23 and 33 are set. Is Hs, Hs−Hr is set to about 10 to 50% of 2δd (that is, δdu + δdl) which is the total clearance of the hydrodynamic bearing 40. If the symbol representing the number of stages of the centrifugal blades is n, and the centrifugal blade stage closest to the gas bearing 40 is n = 1, the blade clearance δ _en of the nth centrifugal blade stage from the gas bearing 40 and (n + 1) The relationship with the blade clearance δ _{en + 1} of the stage centrifugal blade stage is expressed by the following equation.
δ _{en + 1} = δ _en + (Hs−Hr)

  In order to compress gas from ultra-high vacuum to atmospheric pressure, it is necessary to increase the number of blades. Here, when the temperatures of the rotor blades and the stationary blades are compared, the temperature on the rotor blade side is naturally higher. Therefore, if the clearance of each stage is the same when multistage, the difference in thermal expansion between the rotor blade and stationary blade is caused by this temperature difference, the upstream clearance gradually becomes narrower, and the rotor blade and stationary blade are There is a risk of contact. For this reason, the blade clearance at each stage must be adjusted in consideration of this temperature difference. However, since the blade clearance at each stage is very small, measuring and adjusting the clearances at all stages is very laborious and causes an increase in assembly time.

  Therefore, the axial thickness on the stationary blade side is set in advance to be thicker than the axial thickness on the rotating blade side. Then, every time the number of stages is increased, the wing clearance naturally increases. For example, assuming that the axial thickness on the stationary blade side is set to t μm thicker than the axial thickness on the rotor blade side, and the blade clearance of the centrifugal blade stage closest to the gas bearing 40 is CL μm, the next stage The blade clearance becomes CL μm + t μm, and the blade clearance of the next stage becomes CL μm + t μm + t μm. As the number of stages increases, the blade clearance naturally increases. This dimensional difference may be determined in consideration of the temperature difference between the rotary blade side and the fixed blade side. In addition, if the material of the rotary blade and the fixed blade are different, the difference in their linear expansion coefficients may be taken into consideration. The larger the dimensional difference, the larger the upstream clearance and the greater the effect on performance degradation. This dimensional difference is determined from the viewpoints of assemblability, contact reliability, and performance, and is generally set to approximately 10 to 50% of the clearance of the lowermost (atmospheric pressure side) blade.

  FIG. 5 is an enlarged view of a main part showing an exhaust part in which the centrifugal blade element is formed on both the surface forming the axial minute clearance on the rotor blade side and the surface on the opposite side. As shown in FIG. 5, in the turbo vacuum pump of the present embodiment, the centrifugal blade elements 32a and 42a formed of centrifugal blade grooves that compress and exhaust gas in the radial direction form a minute axial clearance on the rotary blade side. And on the opposite surface. In order to increase the number of wings with minute clearances, the accuracy of each part has never been as high as possible. The centrifugal blade elements 32a and 42a formed of centrifugal blade grooves that compress and exhaust gas in the radial direction are formed on a surface that exhausts gas from the inner peripheral side to the outer peripheral side. That is, the centrifugal blade elements 32a and 42a are formed in the direction in which the centrifugal force acts. However, when the centrifugal blade element is formed only on one side, the centrifugal blade surface is likely to be bent and deformed, and the surface needs to be corrected. Here, on the rotor blade side, the same centrifugal blade groove is formed on the surface on the opposite side where the centrifugal blade groove is formed, thereby reducing the bending and deformation of the surface. That is, the centrifugal blade grooves of the centrifugal blade elements 42 a, 22 a, and 32 a are formed on both surfaces of the upper rotational member (upper rotational portion) 42 and the centrifugal blades 22 and 32. In addition, the centrifugal blade groove formed on the opposite side of the surface that exhausts the gas from the inner peripheral side to the outer peripheral side is formed at an angle in the direction of guiding the gas from the outer peripheral side to the inner peripheral side, and also has the effect of compressing the gas is there. However, compared with the compression action of the centrifugal blade groove formed on the regular surface, the compression effect is small because of compression in the direction against the centrifugal force.

  FIG. 6 is an enlarged view of a main part showing a configuration for fastening the centrifugal blade elements arranged in multiple stages in the axial direction. As shown in FIG. 6, in the turbo vacuum pump of this embodiment, an elastically deformable structure 48 is provided in a part of components that fasten the centrifugal blade elements 32 a and 42 a arranged in multiple stages in the axial direction. The elastic deformation structure portion 48 is formed of an annular spacer, and a slit 48s is formed in the elastic deformation structure portion 48 so that the upper and lower portions 48a and 48b are easily deformed.

In the turbo vacuum pump of this embodiment, ceramics are suitable as the material of each component because a very small blade clearance is formed. Silicon nitride ceramics having high strength are suitable for the rotor blade side, and silicon carbide ceramics having high thermal conductivity are suitable for the fixed blade side. In addition, alumina ceramics can also be used on the fixed blade side. Stainless steel (martensitic stainless steel) when a material with a small coefficient of linear expansion (about 3 x ^10-6 / ° C) such as ceramics is used for the rotor blade and stainless steel (martensitic stainless steel) is used for the rotating shaft. Since the linear expansion coefficient is about 10 × 10 ⁻⁶ / ° C., there is a risk that loosening of the fastening may occur during temperature rise due to rotation of the rotating body due to the difference in linear expansion coefficient. Therefore, as shown in FIG. 6, an elastically deformable structure portion 48 is provided on at least a part of the components for fastening the centrifugal blade elements 32a and 42a arranged in multiple stages in the axial direction, and when the rotary blade is fastened in the axial direction, If the elastic deformation structure 48 is deformed in advance in the axial direction as indicated by the broken line in FIG. 6, it is possible to prevent loosening due to thermal deformation. As a material of the elastic deformation structure 48, an aluminum alloy is suitable. Aluminum alloy has a large linear expansion coefficient (23 × 10 ⁻⁶ / ° C.) and is a ductile material.

Next, the configuration of the wing element of the exhaust unit 10 will be described.
FIGS. 7A and 7B are views showing the turbine blade portion 13 of the turbine blade exhaust portion 11. FIG. 7A is a plan view of the turbine blade portion 13 as viewed from the intake port side, showing only the uppermost turbine blade 12 closest to the intake port 5 of the casing 2, and FIG. ) Is a diagram in which a view of the turbine blade 12 seen radially toward the center is partially developed on a plane. As shown in FIGS. 7A and 7B, the turbine blade portion 13 has a boss portion 14 and a turbine blade 12. The turbine blade 12 includes a plurality of plate-like blades 12 a that are radially attached to the outer peripheral portion of the boss portion 14. The boss portion 14 is formed with a hollow portion 15 and a through hole 15h. The blades 12a are attached with a twist angle twisted by β1 (for example, 10 to 40 degrees) from the central axis of the rotary shaft 1. Other configurations of the turbine blade 12 are the same as the configuration of the uppermost turbine blade 12, but the number of blades, the blade attachment angle β1, the outer diameter of the portion of the boss portion 14 to which the blade is attached, and the blade length. These may be changed as appropriate.

  8A, 8B, and 8C are views showing the fixed blade 17 of the turbine blade exhaust section. FIG. 8A is a plan view of the uppermost fixed blade 17 closest to the intake port 5 of the casing 2 as viewed from the intake port side, and FIG. 8B is a diagram in which the fixed blade 17 is radially directed toward the center. FIG. 8C is a cross-sectional view taken along the line VIII-VIII in FIG. 8A. The fixed wing 17 includes an annular ring portion 18 and plate-like blades 17 a that are radially attached to the outer peripheral portion of the annular portion 18. An inner peripheral portion of the annular portion 18 forms a shaft hole 19 through which the rotary shaft 1 (see FIG. 1) passes. The blades 17a are attached with a twist angle twisted by β2 (for example, 10 to 40 degrees) from the central axis of the rotary shaft 1. The structure of the other fixed blades 17 is the same as that of the uppermost fixed blade 17, but the number of blades, the blade mounting angle β 2, the outer diameter of the annular portion, the length of the blades, etc. are appropriately changed. Also good.

  FIGS. 9A and 9B are views showing the centrifugal blade 22 of the first centrifugal blade exhaust unit 21. FIG. 9A is a plan view of the uppermost centrifugal blade 22 closest to the intake port 5 of the casing 2 as viewed from the intake port side, and FIG. 9B is a front sectional view of the centrifugal blade 22. . The centrifugal blade 22, which is a high vacuum side centrifugal blade, includes a substantially disk-shaped base portion 25 having a boss portion 24, and a centrifugal blade element 22 a formed on one surface of the base portion 25. The boss portion 24 is formed with a through hole 24h through which the rotary shaft 1 is inserted. The rotation direction of the centrifugal blade 22 is clockwise in FIG.

  The centrifugal blade element 22a is formed of a spiral centrifugal groove as shown in FIG. The spiral centrifugal groove constituting the centrifugal blade element 22a has a structure extending in the gas flow direction backward (opposite to the rotation direction) with respect to the rotation direction, and from the outer peripheral surface of the boss portion 24 to the outer peripheral edge of the base portion 25. Has reached. The configuration of the other centrifugal blades 22 is the same as the configuration of the uppermost centrifugal blade 22, but the number and shape of the centrifugal grooves, the outer diameter of the boss portion, the length of the flow path formed by the centrifugal grooves, etc. You may change suitably.

  FIGS. 10A and 10B are views showing the centrifugal blade 32 of the second centrifugal blade exhaust part 31. FIG. 10A is a plan view of the uppermost centrifugal blade 32 closest to the intake port 5 of the casing 2 as viewed from the intake port side, and FIG. 10B is a front sectional view of the centrifugal blade 32. . The centrifugal blade 32, which is a centrifugal blade on the atmospheric pressure side, includes a substantially disc-shaped base portion 35 and a centrifugal blade element 32 a formed on one surface of the base portion 35. The base portion 35 is formed with a through hole 35h through which the rotary shaft 1 is inserted. The rotation direction of the centrifugal blade 32 is clockwise in FIG.

  The centrifugal blade element 32a is formed of a spiral centrifugal groove as shown in FIG. The spiral centrifugal groove constituting the centrifugal blade element 32a has a structure extending in the gas flow direction backward (opposite to the rotation direction) with respect to the rotation direction, and from the inner peripheral portion of the substantially disc-shaped base 35. It reaches the outer periphery. Other configurations of the centrifugal blade 32 are the same as the configuration of the uppermost centrifugal blade 32, but the number and shape of the centrifugal grooves, the length of the flow path formed by the centrifugal grooves, and the like may be appropriately changed.

  As shown in FIGS. 9 and 10, when the centrifugal blade 32 on the atmospheric pressure side and the centrifugal blade 22 on the high vacuum side are compared, the groove depth of the centrifugal blade element 32a in the centrifugal blade 32 on the atmospheric pressure side is shallow (or The height of the groove of the centrifugal blade element 22a in the centrifugal blade 22 on the high vacuum side is set deep (or the height of the convex portion is high). In other words, the groove depth of the centrifugal groove of the centrifugal blade element becomes deeper (or the height of the convex portion becomes higher) as it goes to higher vacuum. In short, the exhaust speed increases as it goes to the high vacuum side.

  Next, the bearing motor unit 50 will be described. As shown in FIG. 1, the bearing motor unit 50 includes a motor 51 that applies a rotational driving force to the rotary shaft 1, an upper radial magnetic bearing 53 that supports the rotary shaft 1 in the radial direction, a lower radial magnetic bearing 54, and a rotating body. Is provided with an upper thrust magnetic bearing 56 that attracts the shaft in the axial direction. The motor 51 is composed of a high frequency motor. The upper radial magnetic bearing 53, the lower radial magnetic bearing 54, and the upper thrust magnetic bearing 56 are all active magnetic bearings. An upper protective bearing 81 that supports the rotating shaft 1 in the radial direction and the axial direction in order to prevent the rotating blade and the fixed blade from coming into contact with each other when an abnormality occurs in any of the magnetic bearings 53, 54, and 56. And a lower protective bearing 82 are provided. The upper thrust magnetic bearing 56 is configured to attract the target disk 58 with an electromagnet.

Next, the operation of the turbo vacuum pump configured as shown in FIGS. 1 to 10 will be described.
As the turbine blade 12 in the turbine blade exhaust section 11 rotates, gas is introduced in the axial direction from the intake port 5 of the pump. By using the turbine blade 12, the exhaust speed can be increased, and a relatively large amount of gas can be exhausted. The gas introduced from the intake port 5 passes through the uppermost turbine blade 12 and is decelerated by the fixed blade 17 to increase the pressure. Similarly, the turbine blades 12 and the fixed blades 17 on the downstream side are exhausted in the axial direction, and the pressure rises.

  The gas flowing into the first centrifugal blade exhaust portion 21 from the turbine blade exhaust portion 11 is introduced into the uppermost centrifugal blade 22, and the interaction between the uppermost centrifugal blade 22 and the uppermost stationary blade 23, that is, the gas concerned. By the drag action due to the viscosity of the centrifugal blade and the centrifugal action caused by the rotation of the centrifugal blade element 22a, the gas is compressed and exhausted along the surface of the base portion 25 of the centrifugal blade 22 toward the outer peripheral side. That is, the gas introduced into the uppermost centrifugal blade 22 is introduced into the centrifugal blade 22 in the substantially axial direction 27 in FIG. 9B, and is centrifuged toward the outer periphery through the spiral centrifugal groove. Flows in direction 28, is compressed and exhausted.

  The gas compressed toward the outer peripheral side by the uppermost centrifugal blade 22 flows into the uppermost stationary blade 23, and changes its direction in the substantially axial direction by the inner peripheral surface extending in the vertical direction of the stationary blade 23, It flows into a space provided with a spiral guide (not shown) on the surface side of the fixed wing 23. Then, when the uppermost centrifugal blade 22 rotates, the uppermost stationary blade 23 is dragged by the gas viscosity between the spiral guide of the fixed blade 23 and the back surface of the base 25 of the uppermost centrifugal blade 22. The gas is compressed and exhausted toward the inner peripheral side along the surface. The gas that has reached the inner peripheral side of the uppermost stationary blade 23 changes its direction in the substantially axial direction by the outer peripheral surface of the boss portion 24 of the uppermost centrifugal blade 22 and is introduced into the downstream centrifugal blade 22. The gas is compressed and exhausted by the centrifugal blade 22 and the fixed blade 23 on the downstream side.

  The gas flowing into the second centrifugal blade exhaust portion 31 from the first centrifugal blade exhaust portion 21 is introduced into the uppermost centrifugal blade 32, and the interaction between the uppermost centrifugal blade 32 and the uppermost fixed blade 33, that is, By the drag action due to the viscosity of the gas and the centrifugal action caused by the rotation of the centrifugal blade element 32a, the gas is compressed and exhausted toward the outer peripheral side along the surface of the base 35 of the uppermost centrifugal blade 32. Next, a spiral guide (not shown) that flows into the uppermost fixed blade 33 and changes its direction substantially in the axial direction by the inner peripheral surface extending in the vertical direction of the fixed blade 33 and is on the surface side of the fixed blade 33. It flows into the established space. Then, when the uppermost centrifugal blade 32 rotates, the drag action caused by the gas viscosity between the spiral guide (not shown) of the fixed blade 33 and the back surface of the base 35 of the uppermost centrifugal blade 32 causes the most. The gas is compressed and exhausted toward the inner peripheral side along the surface of the upper fixed wing 33. The gas that has reached the inner peripheral side of the uppermost fixed blade 33 changes its direction substantially in the axial direction, and is introduced into the centrifugal blade 32 on the downstream side. The gas is compressed and exhausted by the centrifugal blade 32 and the fixed blade 33 on the downstream side. And the gas discharged | emitted from the 2nd centrifugal blade exhaust part 31 is discharged | emitted from the exhaust port 6 to the exterior of a vacuum pump.

FIG. 11 is a graph showing a performance comparison according to blade clearance in a turbo type vacuum pump. FIG. 11 is a diagram showing a relationship between a differential pressure that can be acquired by one stage of a centrifugal blade and a rotational speed when the exhaust pressure is 760 Torr. In FIG. 11, the horizontal axis represents the rotational speed (min ⁻¹ ) of the vacuum pump, and the vertical axis represents the differential pressure (Torr). A comparison is made between the case where the blade clearance is 25 μm and the case where the blade clearance is 40 μm. As shown in FIG. 11, when the blade clearance is 25 μm, a differential pressure of about 300 Torr can be obtained at a rotational speed of 100,000 revolutions per minute (min ⁻¹ ) with one stage of the centrifugal blade. On the other hand, when the blade clearance is 40 μm, a differential pressure of about 250 Torr can be obtained at a rotational speed of 100,000 revolutions per minute (min ⁻¹ ) with one stage of the centrifugal blade. That is, when the blade clearance changes by 15 μm from 25 μm to 40 μm, the performance decreases as shown in the graph. This also shows the effect of the present invention in which the blade clearance can be set minutely.

  FIG. 12 is a longitudinal sectional view showing another embodiment of the turbo vacuum pump according to the present invention. As shown in FIG. 12, the turbo vacuum pump includes a thrust magnetic bearing 55 that acts in a direction to cancel the thrust force generated by the differential pressure between the exhaust side and the intake side due to the exhaust action of the exhaust unit 10. The thrust magnetic bearing 55 includes an upper thrust magnetic bearing 56 having an electromagnet, a lower thrust magnetic bearing 57 having an electromagnet, and a target disk 58 fixed to the lower portion of the rotary shaft 1. In the thrust magnetic bearing 55, the target disk 58 is sandwiched between the upper and lower thrust magnetic bearings 56, 57, the target disk 58 is attracted by the electromagnets of the upper and lower thrust magnetic bearings 56, 57, and the exhaust side by the exhaust action of the exhaust unit 10 The thrust force generated by the differential pressure on the intake side is canceled out. The other configuration of the turbo vacuum pump shown in FIG. 12 is the same as that of the turbo vacuum pump shown in FIG.

In the present invention, an example in which a magnetic bearing is used as the radial bearing has been shown, but it may be a gas bearing. The present invention is also for obtaining an effect in the atmospheric pressure region. Even if at least one of a cylindrical thread groove rotor, a centrifugal blade, and a turbine blade, which is conventionally employed in a turbo molecular pump, is used on the upstream side of the blade element in the atmospheric pressure region at a vacuum of approximately 10 Torr or less, Of course it does not matter. The centrifugal blade used in this region has the same exhaust principle as the microclearance centrifugal blade of the present invention, but has a higher degree of vacuum and less backflow than the atmospheric pressure region. The blade clearance of the general-purpose turbo molecular pump (about 0.1 to 1 mm) may be used. When this centrifugal blade is made of an aluminum alloy, it is of course possible to provide the elastically deformable structure shown in FIG.
Whether the gas bearing is a dynamic pressure type or a static pressure type, the effect of the present invention is not affected. In the case of the static pressure type, an external gas supply means is required.

FIG. 1 is a longitudinal sectional view showing an embodiment of a turbo vacuum pump according to the present invention. FIG. 2 is an enlarged view of a main part showing the gas bearing and its peripheral part. 3 is a view taken in the direction of arrow III in FIG. FIG. 4 is an enlarged view of the main part showing the exhaust part set so that the blade clearance gradually increases from the exhaust side toward the intake side. FIG. 5 is an enlarged view of a main part showing an exhaust part in which the centrifugal blade element is formed on both the surface forming the axial minute clearance on the rotor blade side and the surface on the opposite side. FIG. 6 is an enlarged view of a main part showing a configuration for fastening the centrifugal blade elements arranged in multiple stages in the axial direction. 7 (a) and 7 (b) are views showing the turbine blade portion of the turbine blade exhaust portion, and FIG. 7 (a) is a plan view of the turbine blade portion as viewed from the intake port side. FIG. 7B is a diagram showing only the uppermost turbine blade closest to the mouth, and FIG. 7B is a diagram in which a view of the turbine blade radially viewed toward the center is partially developed on a plane. FIGS. 8A, 8B, and 8C are diagrams showing the fixed blades of the turbine blade exhaust section, and FIG. 8A shows the uppermost fixed blade closest to the intake port of the casing at the intake port. 8B is a plan view seen from the side, and FIG. 8B is a diagram in which a view of the fixed wing viewed radially toward the center is partially developed on the plane, and FIG. It is the VIII-VIII sectional view taken on the line of (a). FIGS. 9A and 9B are views showing the centrifugal blades of the first centrifugal blade exhaust section, and FIG. 9A shows the uppermost centrifugal blade closest to the intake port of the casing from the intake port side. FIG. 9 (b) is a front sectional view of the centrifugal blade. 10 (a) and 10 (b) are views showing the centrifugal blade of the second centrifugal blade exhaust part, and FIG. 10 (a) shows the uppermost centrifugal blade closest to the intake port of the casing from the intake port side. FIG. 10 (b) is a front sectional view of the centrifugal blade. FIG. 11 is a graph showing a performance comparison according to blade clearance in a turbo type vacuum pump. FIG. 11 is a diagram showing a relationship between a differential pressure that can be acquired by one stage of a centrifugal blade and a rotational speed when the exhaust pressure is 760 Torr. FIG. 12 is a longitudinal sectional view showing another embodiment of the turbo vacuum pump according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Casing 3 Upper casing 4 Lower casing 5 Intake port 6 Exhaust port 10 Exhaust part 11 Turbine blade exhaust part 12 Turbine blade 13 Turbine blade part 14 Boss part 15 Hollow part 15h Through-hole 16 Bolt 17 Fixed blade 18 Spacer 21 1st 1 centrifugal blade exhaust part 22 centrifugal blades 22a, 32a, 42a centrifugal blade element 23 fixed blade 24 boss part 24h through hole 25 base 31 second centrifugal blade exhaust part 32 centrifugal blade 33 fixed blade 35 base 35h through hole 40 gas bearing 41 fixed Side member (fixed side part)
42 Upper rotation side member (upper rotation side part)
43 Lower rotation side member (lower rotation side part)
45 spiral groove 48 elastic deformation structure part 48s slit 50 bearing motor part 51 motor 53 upper radial magnetic bearing 54 lower radial magnetic bearing 55 thrust magnetic bearing 56 upper thrust magnetic bearing 57 lower thrust magnetic bearing 58 target disk 81 upper protection bearing 82 lower protection bearing

Claims (5)

A rotating shaft extending over substantially the entire length of the pump; an exhaust section formed by alternately arranging rotating blades and fixed blades in the casing; a motor for applying a rotational driving force to the rotating shaft; and the rotating shaft In a turbo type vacuum pump having a bearing motor portion having a bearing that is rotatably supported,
A gas bearing is used as a bearing for supporting the rotating shaft in the thrust direction, spiral grooves are formed on both surfaces of a fixed side portion of the gas bearing, and an upper rotating side portion and a lower rotating side portion fixed to the rotating shaft, By sandwiching the fixed side portion where the spiral groove is formed,
A turbo type vacuum pump characterized in that a centrifugal blade element for compressing and exhausting gas in a radial direction is formed on a surface opposite to the surface facing the spiral groove in the upper rotation side portion.   The centrifugal blade elements that compress and exhaust the gas in the radial direction are arranged in multiple stages in the axial direction, and the blade clearance of the centrifugal blade elements is set so as to gradually increase from the exhaust side toward the intake side. Item 2. A turbo vacuum pump according to item 1.   Centrifugal blade elements for compressing and exhausting gas in the radial direction are arranged in multiple stages in the axial direction, and the axial thickness of the fixed blade with respect to the axial thickness of the rotary blade having the centrifugal blade element is set in the axial direction. 2. The turbo vacuum pump according to claim 1, wherein the turbo-type vacuum pump is formed to be about 10 to 50% thicker than the blade clearance formed in the casing.   4. A centrifugal blade groove of a centrifugal blade element that compresses and exhausts gas in a radial direction is formed on both a surface that forms a minute clearance in the axial direction on the rotor blade side and a surface on the opposite side thereof. The turbo type vacuum pump according to any one of the above.   The turbo type vacuum pump according to any one of claims 1 to 4, wherein an elastically deformable structure portion is provided on at least a part of a part for fastening the centrifugal blade elements arranged in multiple stages in the axial direction.

Images